Difference Between Armature and Bone Layers?
So...You could be referring to a few things, but I'm just going to run through all of them real quick.

Armature Scene Layer: The layer in which the armature is in the scene.  This matters for rendering and viewport filtering.

Armature Layers: The Bone Layers in an Armature.  Activating a Layer makes it visible in the editor.

Armature Protected Layers: Runs parallel to the Armature layers, activating this layer makes the corresponding Armature Layer write-protected.  Users will be unable to edit bones that are in this layer.

Bone layers: Armature Layers from the perspective of bones.  Determines which armature layer(s) a bone resides in.